<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="6.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Surzhykov, A.</style></author><author><style face="normal" font="default" size="100%">Santos, J. P.</style></author><author><style face="normal" font="default" size="100%">Amaro, P</style></author><author><style face="normal" font="default" size="100%">Indelicato, P.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Negative-continuum effects on the two-photon decay rates of hydrogenlike ions</style></title><secondary-title><style face="normal" font="default" size="100%">Physical Review A (Atomic, Molecular, and Optical Physics)</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">atomic structure</style></keyword><keyword><style  face="normal" font="default" size="100%">Dirac equation</style></keyword><keyword><style  face="normal" font="default" size="100%">hydrogen neutral atoms</style></keyword><keyword><style  face="normal" font="default" size="100%">perturbation theory</style></keyword><keyword><style  face="normal" font="default" size="100%">relativistic corrections</style></keyword><keyword><style  face="normal" font="default" size="100%">spontaneous emission</style></keyword><keyword><style  face="normal" font="default" size="100%">uranium</style></keyword><keyword><style  face="normal" font="default" size="100%">xenon</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://link.aps.org/abstract/PRA/v80/e052511</style></url></web-urls></urls><number><style face="normal" font="default" size="100%">5</style></number><publisher><style face="normal" font="default" size="100%">APS</style></publisher><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">052511</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Two-photon decay of hydrogenlike ions is studied within the framework of second-order perturbation theory, based on the relativistic Dirac's equation. Special attention is paid to the effects arising from the summation over the negative-energy (intermediate virtual) states that occur in such a framework. In order to investigate the role of these states, detailed calculations have been carried out for the 2s1/2--&gt;1s1/2 and 2p1/2--&gt;1s1/2 transitions in neutral hydrogen H as well as for hydrogenlike xenon Xe53+ and uranium U91+ ions. We found that for a correct evaluation of the total and energy-differential decay rates, summation over the negative-energy part of Dirac's spectrum should be properly taken into account both for high-Z and low-Z atomic systems.</style></abstract></record></records></xml>